The present invention relates generally to methods for cleaning piping systems and equipment, and, more particularly, to methods for cleaning piping systems and equipment that supply or transport aqueous gelatin based solutions, such as those used in the manufacture of photosensitive media.
The manufacture of photosensitive media utilizes liquid transfer systems, which are commonly called solution delivery systems for the delivery of various chemicals and emulsions. The solution delivery system consists of permanent (pumps, sensors, etc.) equipment and semi-permanent equipment (hoses, gaskets, etc.). Once a solution delivery system has completed delivering liquid formulations and/or solutions for a particular product, the system must be purged and cleaned in preparation for the manufacture of a subsequent and different product.
Many methods are used to clean the solution delivery system in preparation for the subsequent product. These methods include both off-line and in-situ methods. Off-line methods may include, but are not limited to, complete disassembly and hand cleaning, complete disassembly and parts washing (automated parts washer), complete disassembly and disposal of xe2x80x9csomexe2x80x9d system components, etc. In-situ methods may include, but are not limited to, xe2x80x9cpigxe2x80x9d cleaning, automated on-line cleaning, etc.
Off-line cleaning options (disassembly, etc.) typically require an extensive amount of time to complete. In these methods, there is also the potential for equipment to be re-assembled improperly which could lead to liquid waste and machine downtime.
Numerous chemical cleaning solutions exist for off-line cleaning of removed components. Depending on the number of parts and their size, the parts can be either hand cleaned (using scrub brushes, etc.) or cleaned in xe2x80x9cparts washers.xe2x80x9d Parts washers are well known apparatus that clean parts via immersion, spray cleaning, and even ultrasonic methods to clean the parts. These cleaning enhancement methods can be employed with virtually any chemical cleaning solution.
On-line cleaning techniques have the advantages of: less machine downtime and less manpower to execute a cleaning operation of a solution delivery system.
In methods such as xe2x80x9cpigxe2x80x9d cleaning, there is still some operator intervention required and it is difficult to clean the entire delivery system because a xe2x80x9cpig launcherxe2x80x9d and xe2x80x9cpig receiverxe2x80x9d are required. In addition, xe2x80x9cpigxe2x80x9d cleaning may also utilize xe2x80x9cballxe2x80x9d valves, which are not sanitary valves.
Clean-In-Place cleaning techniques can utilize a variety of different cleaning solutions and the method of introduction of those cleaning solutions can be automated to a variety of different levels. Clean-In-Place technologies have the advantage of being completely automated and can utilize sanitary valves such as those used in the pharmaceutical industry (e.g. diaphragm valves, balloon valves, etc.). The problem with Clean-In-Place technologies is that a series or sequence of cleaning solutions must be identified that can efficiently clean the fouling left by all product solutions that are delivered through the solution delivery system.
It is therefore an object of the present invention to provide a method for cleaning-in-place piping systems and equipment that supply or transport aqueous gelatin based solutions, such as those used in the manufacture of photosensitive media.
It is a further object of the present invention to provide a clean-in-place methodology that is capable of removing the fouling from aqueous, gelatin-based, sensitizing solutions.
Yet another object of the present invention is to provide a clean-in-place method that is capable of removing the numerous constituents in the adsorbed fouling as well as addressing the absorption fouling associated with polymeric materials in the solution delivery system.
Still another object of the present invention is to provide a clean-in-place method that is capable of cleaning photographic chemistry product fouling including a proteinaceous portion and a non-proteinaceous portion from the delivery system.
Briefly stated, the foregoing and numerous other features, objects and advantages of the present invention will become readily apparent upon a review of the detailed description, claims and drawings set forth herein. These features, objects and advantages are accomplished by practicing a method comprising the steps of displacing resident product solution in the piping with water, hydrodynamically cleaning the piping system using two-phase flow a first time, chemically cleaning the piping system with an aqueous bleach solution to remove the proteinaceous portion of the photographic chemistry product fouling, chemically cleaning the piping system with a functionalized ethyl acetate solvent to remove the non-proteinaceous portion of the photographic chemistry product fouling, and hydrodynamically cleaning the piping system using two-phase flow a second time after the chemical cleaning steps to remove remaining residue. Preferably, after the second hydrodynamic two-phase flow cleaning step, the delivery system is subjected to a high purity water rinse.
The first chemical cleaning step is performed with a dilute sodium hypochlorite solution. The second chemical cleaning step is performed with a functionalized ethyl acetate solvent. The water flushing and initial two-phase flow cleaning step remove water-soluble fouling through dilution and mass transfer. Chemical cleaning removes water insoluble fouling which is left by aqueous, gelatin-based, sensitizing solutions. The dilute sodium hypochlorite solution attacks the protein that is left by the product solution. The functionalized ethyl acetate solution is used to clean a variety of residuals, including: latex solutions, coupler solvents, etc. In addition, the functionalized ethyl acetate solution also removes absorption fouling that exists in polymeric solution delivery system materials (hoses, gaskets, etc.). The secondary two-phase flow cleaning is utilized to remove any residual fouling that the chemical cleaning solution loosened but did not remove. Finally, the high purity water flush is used to temper the solution delivery system to the appropriate coating temperature and put the highest quality water in the delivery system prior to inserting the next product solution.